I have been using Colin Morris at Cardinal for some time now. He manages all of my credit control. He make and takes calls in my name as if he's calling from my office. The clients have got to know him and he keeps on top of the debtor book so that I have significantly better cashflow and he spots errors we make in invoicing and so on and prevents us from upsetting clients.
The clients in turn will call him if they have issues with invoices and he is now an essential part of our invoicing process and he costs a loot less than an equivalent part time member of staff. I don't regret using him and clients now have a professional Credit Manager to talk to.